Solar Influences Data Center (SIDC) / RWC Belgium Royal Observatory of Belgium E-mail: Pierre.Cugnon@oma.be http://sidc.oma.be SIDC WEEKLY BULLETIN -------------------- WEEK 122 from 2003 Apr 28 SOLAR ACTIVITY -------------- The solar activity was mostly low, despite the fact that several active regions developed a beta-gamma configuration. The dominant active region was Catania#84 (NOAA0349), which grew on the first 4 days of the period, then stabilized, but only produced a few C-flares. Only two M1 flares occured over the period. A small low latitude latitude coronal hole was in a geoeffective position in the Western hemisphere, and it was responsible for most of the enhanced geomagnetic activity of this week. Another much larger trans-equatorial coronal hole was rotating into the Western hemisphere at the end of the period. Early this week, active region Catania#84 (NOAA0349) will rotate behind the West limb and no major active region has appeared recently in the East. Therefore, solar activity is expected to remain at low levels for the next few days. GEOMAGNETIC ACTIVITY -------------------- The geomagnetic activity was high during the first five days of the period, in association with a high speed solar wind stream (max speed 650km/s on May 1st). Minor to major storms occured on April 28, 01:00 to 06:00UT, April 29 12:00 to April 30 04:00UT, April 30 late to May 1 early, and a brief episode early on May 2. During the last two days, the solar wind speed decreased to 400km/s, with a stable northward orientation of the interplanetary magnetic field. The geomagnetic conditions then became quiet to unsettled. Because of the influence of a new bigger coronal hole, the geomagnetic activity is expected to rise again this week, from May 6 and for 3 to 5 days, reaching active or minor storm levels. --------------------------------------------------------------------------- DAILY INDICES DATE RC 10CM Ak BKG M X 2003 Apr 28 173 152 016 B5.7 0 0 2003 Apr 29 173 155 026 B5.8 1 0 2003 Apr 30 153 154 041 B4.2 0 0 2003 May 01 149 149 035 B5.2 0 0 2003 May 02 106 144 016 B3.6 1 0 2003 May 03 135 148 012 B5.5 0 0 2003 May 04 156 142 008 B5.8 0 0 # RC : Sunspot index from Catania Observatory (Italy) # 10cm: 10.7 cm radioflux (DRAO, Canada) # Ak : Ak Index Wingst (Germany) # BKG : Background GOES X-ray level (NOAA, USA) # M,X : Number of X-ray flares in M and X class, see below (NOAA, USA) --------------------------------------------------------------------------- NOTICEABLE EVENTS DAY BEGIN MAX END LOC XRAY OP 10CM TYPE Cat NOAA NOTE 29 0432 0459 0510 S12W55 M1.1 1F 71 0337 CME 02 0247 0308 0344 S17W18 M1.0 79 0345